Microplastics in The Human Body

Researchers announce the discovery of microplastics traveling in the bloodstream of anonymous donors and embedded deep in the lung tissue of patients awaiting surgery.  Another study reported finding microplastics in placentas.
These discoveries have made for a wobbly series of headlines that some might find concerning, but the science remains far from settled.

Microplastics in The Human Body
By Pierre Mouchette | Bits-n-Pieces

Research makes it clear that microplastics are ubiquitous.  These particles enter peoples’ bodies regularly during inhalation or through the consumption of food or drinks, and they find their way into our vital body systems.  What remains less apparent is what health risks, if any, these tiny particles pose at the concentrations they have been found.  Scientists say the outbreak of recent studies and their headlines represents their first steps toward understanding these particles' impact on our daily lives.  
Scientists have identified microplastics in the air we breathe and have found microplastics in the lungs.  “But does it matter that there is plastic in our lungs?  We do not know the answer to that question at the moment.”
 
What is a microplastic?
Studies indicate that microplastics are in the air we breathe, the dust accumulating on our floors, and the seafood we buy at the grocery store.  There is no single definition for microplastic, but researchers generally state that it is often smaller than the tiniest grain of sand or a fraction of the width of a human hair.  The particles' shape, size, and chemical composition also vary, and researchers typically focus on identifying the most common polymers. 
The smallest particles concern the researchers the most.  They are more likely to penetrate deeply into the body and pass through the protective membranes within.  Finding microplastics within the body takes meticulous, careful work.  The risk of contamination is ever-present.
 
Findings
Much of the research on microplastics has been studied with a relatively small number of samples focused on identifying microplastics and determining exposure.  Among the most thought-provoking findings are microplastics in the lung tissue of living people, the discovery of microplastics in the bloodstream, and the fact that infants might be among those most often exposed.
 
Many questions remain unanswered.
The plastic circulating in our bodies,  “Are they excreted?  What is the fraction excreted?  Are they stuck somewhere in the system?  Do they accumulate in certain organs?  Do they pass the blood-brain barrier or the placenta?”
 
Future research
Studies involving animals or cells grown in laboratory environments suggest microplastics could cause inflammatory responses, oxidative stress, and cell damage.  “Exposure is now apparent.  The question is, how toxic are they, and at what level are they toxic?”